The following Patent Documents 1 to 5 disclose iron-type golf club heads. Each of these iron type golf club heads has a face portion with a front surface for hitting a ball. The face portion is provided in its peripheral edge with a flange portion protruding backwardly of the head. The flange portion is formed annularly in a rear surface of the face portion so as to define a cavity (cavity back iron). Since a part of the face portion corresponding to the cavity has a small thickness, the face portion is easy to be bent and produces high rebound performance.
The flange portion may be provided in its inner surface side facing to the cavity with a concave part dented toward the outside of the head. Such concave part forms a so-called undercut cavity. In such a golf club head, the region of the cavity is expanded toward the outside of the head, and a sweet area where the high rebound performance is produced is widened.